Add multi-release: true to jar artifcats

Required, due to log4j2 included in ProGuardCORE 8.0.0

ant/build.gradle

@@ -40,6 +40,7 @@ task fatJar(type: ShadowJar) {
     manifest {
         attributes(
                 'Manifest-Version': '1.0',
+                'Multi-Release': true,
                 'Implementation-Version': archiveVersion.get())
     }
 }

base/build.gradle

@@ -42,7 +42,13 @@ dependencies {
     }
 }
 
-jar.manifest.attributes('Implementation-Version': version)
+jar {
+    manifest {
+        attributes(
+                'Multi-Release': true,
+                'Implementation-Version': archiveVersion.get())
+    }
+}
 
 // Early access automatic downloads are not yet supported:
 // https://github.com/gradle/gradle/issues/14814

gui/build.gradle

@@ -41,6 +41,7 @@ task fatJar(type: ShadowJar) {
         attributes(
                 'Manifest-Version': '1.0',
                 'Main-Class': 'proguard.gui.ProGuardGUI',
+                'Multi-Release': true,
                 'Implementation-Version': archiveVersion.get())
     }
 }

proguard-app/build.gradle

@@ -27,6 +27,7 @@ task fatJar(type: ShadowJar) {
     manifest {
         attributes(
                 'Main-Class': 'proguard.ProGuard',
+                'Multi-Release': true,
                 'Implementation-Version': archiveVersion.get())
     }
 }

retrace/build.gradle

@@ -38,6 +38,7 @@ task fatJar(type: ShadowJar) {
     manifest {
         attributes(
                 'Manifest-Version': '1.0',
+                'Multi-Release': true,
                 'Main-Class': 'proguard.retrace.ReTrace')
     }
 }